Computer Aided Design/Computer Aided Manufacture (CAD/CAM) technology was firstly introduced to the design and manufacture of fixed dental restoration by French professor Francois Duret in the early 70s of 20th century, and it triggered a significant technical revolution in dental restoration field. Whereby, CAD refers to the product design process in which computer is utilized to generate or handle various digital and graphical information; CAM refers to the product manufacturing process performed by CNC (Computer Numerical Control) machining equipment, such as automatic processing and shaping CNC milling machine. Currently, CAD/CAM can be utilized to fabricate various fixed dental restorations, such as inlay, veneer, bridge, and fixed bridge. Nevertheless, patients usually need to pay 2-3 visits to hospital for accomplishing the whole session; such frequent and complex revisit brings tremendous inconvenience for patient. With the development of computer technology, Chair-Side Dental CAD/CAM is now available for rapid treatment.
In Chair-side Dental CAD/CAM system, the CAD/CAM equipment is placed next to dental chair. After tooth preparation by dentist, the tooth model of patient is achieved through digital technology. Through computer, the data can be analyzed, and the denture (restoration) is designed. Finally, the restoration can be automatically fabricated through milling machine. It will only take about 30 minutes for a patient to accomplish the whole treatment course, and complex further consultation can be avoided. In Chair-side Dental CAD/CAM system, the temporary restoration is no longer necessary, and the dental restoration can be prepared directly. Therefore, the demand for clinic visit is reduced, and the quality of dental restoration is obviously improved. By means of model scanning, both design and manufacture of restoration can be performed and accomplished via digital technology, thus, the restoration can be achieved more precisely and accurately, and the success rate of restoration treatment is enhanced. Problems caused by PFM (Porcelain Fused to Metal) denture and removable denture, such as gingival discoloration and marginal unfitness, are largely reduced, and the patient satisfaction for treatment effect is remarkably improved.
The development of Chair-side Dental CAD/CAM technology brings higher requirements for related dental materials. Not only should the material have favorable machinability, thus, the milling time for materials can be shut down to 20 minutes, but also, the time for after-milling process should be very short, thus, the whole restoration treatment can be finished in one doctor appointment. Although traditional zirconia all-ceramic restoration material is also machinable for CAD/CAM system (Non-Chair-side ones), but it is impossible to accomplish the seat of dental restoration in a single doctor visit time due to 6-8 hours sintering time after milling. Presently, dental material used for Chair-side Dental CAD/CAM, developed or being developed, includes glass ceramic (feldspar, leucite, and lithium silicate glass ceramic) and composite material. The composite material is composed of polymer and filler, and it is a relatively ideal dental restoration material due to its favorable toughness, machinability, wear resistance, and X-ray resistance. However, composite materials in prior art are monochromatic. As for nature tooth, color gradually changes from cervical portion to incisal portion. Compared with nature tooth, dental restoration fabricated from monochrome composite cannot repeat the gradient color of nature tooth and thus is short of aesthetic effect.